In percutaneous transluminal coronary angioplasty (PTCA) procedures a guiding catheter is advanced in the patient's vasculature until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is advanced out of the distal end of the guiding catheter into the patient's coronary artery until the distal end of the guidewire crosses a lesion to be dilated. A dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient's coronary anatomy over the guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with inflation fluid one or more times to a predetermined size at relatively high pressures so that the stenosis is compressed against the arterial wall and the wall expanded to open up the vascular passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter and the guidewire can be removed therefrom.
In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate of angioplasty alone and to strengthen the dilated area, physicians now normally implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel or to maintain its patency. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded within the patient's artery to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion. See for example, U.S. Pat. No. 5,507,768 (Lau et al.) and U.S. Pat. No. 5,458,615 (Klemm et al.), which are incorporated herein by reference.
An essential step in effectively performing a PTCA or stent delivery procedure is properly positioning the balloon catheter at a desired location within the coronary artery, typically by sliding the catheter through a guiding catheter and over a guidewire within the patient's vasculature. In the design of catheter shafts, the trend has been towards minimizing the shaft diameter, to allow the shaft to be advanced further distally within the patient's vascular and to improve the shaft flexibility, resulting in a relatively small gap between the guidewire and the inner surface of the shaft. This relatively small gap exacerbates the problem of guidewire hang-up, i.e., an inability to freely slide the guidewire within the guidewire lumen, especially in a complex procedure or in a long procedure requiring many guidewire or catheter exchanges. Conventional intravascular catheters have commonly included an inner liner formed of a lubricious material such as Teflon or high density polyethylene (HDPE) to facilitate slidably advancing the catheter relative to the guidewire by reducing the frictional force of the guidewire against the inner surface of the shaft. However, one difficulty has been the tendency of small agglomerations of blood and contrast media within the guidewire lumen and adhering to the inner surface of the shaft, especially in complex or long procedures, making it difficult to advance or retract the catheter relative to a guidewire therein. Although anticoagulants such as heparin are commonly used to decrease the coagulation, it can be harmful to administer excessive amounts of anticoagulant during the sometimes lengthy procedure times required.
Accordingly, it would be a significant advance to provide a catheter with a relatively low profile shaft which nonetheless prevented or minimized guidewire hang-up, especially in a complex procedure or a long procedure requiring many guidewire or catheter exchanges. This invention satisfies these and other needs.